1. Field of the Invention
This invention pertains to a coated abrasive belt having a backing comprising a hot-melt adhesive therein, and a method of making the same.
2. Description of the Related Art
The manufacture of coated abrasive belts typically includes the joining (i.e., splicing) together of two free ends of an elongated coated abrasive strip to form an endless belt. Two types of joints are commonly used to splice the ends of the elongated strip together. The two most common types of splices used to Join the ends of the elongated coated abrasive strips are known as a "lap splice" and a "butt splice."
A lap splice is formed by removing the abrasive layer from one end of the coated abrasive strip (i.e., skiving) or, in some cases, from both ends of the coated abrasive strip (i.e., double skiving), coating one or both ends of the strip with a suitable adhesive and then overlapping the ends to form a splice. The preparation of lap splices is disclosed, for example, in U.S. Pat. Nos. 1,009,709, 2,445,807, 3,037,852, and 3,643,387. The drawback of lap splices is that the joint formed is generally somewhat stiffer than the rest of the belt, a condition which predisposes the splice to failure by delamination during use of the belt. Moreover, a lap splice is usually slightly thicker than the rest of the belt which causes "bumping" or "chattering" of the belt during use, a phenomena which is particularly aggravating for the operator of the machine. Furthermore, belts having a lap splice are recommended to be run in one direction in order to minimize the chances of snagging the uppermost layer of the belt.
A "butt splice" is a Joint which is formed by bringing the free ends of the belt together without overlap and securing the ends, for example, by means of a patch or strip of material. (e.g., tape) over the ends of the belt opposite the abrasive layer or by incorporation of a strip of material into a portion of the backing which bridges the ends. The preparation of butt splices is disclosed, for example, in U.S. Pat. Nos. 766,930, 1,588,255, 1,728,673, 2,391,731, 2,733,181, 2,794,726, 3,154,897, 3,402,514, and 3,427,765. Although coated abrasive belts having a butt splice can be run in either direction, such belts still suffer from many of the disadvantages inherent in belts incorporating lap splices. For example, the material used to attach the ends of the coated abrasive strip frequently produces a raised area over the joint which causes premature loss of abrasive material in that region, and also causes formation of grooves in the workpiece. Moreover, such splices tend to wear out at the end portions causing them to split and pull away from each other under the stresses and strains the belt is subjected to during use. This tendency to wear out the end portions of the belt is particularly problematic when sanding or polishing hard substrates such as glass, marble, or granite. Further, a butt splice having a raised area causes the belt to "bump" or "chatter" during use of the belt on an abrading machine comprising a back support, platen, or wheel.
U.S. Pat. No. 3,333,372 discloses an abrasive belt comprising:
a flexible base sheet including an inner face and an outer face, PA1 a layer of finely divided abrasive particles adhesively secured to the outer surface, PA1 the flexible base sheet having end portions abutting each other to form a closed, continuous loop, PA1 a film of flexible adhesive material on the inner surface of the flexible base sheet, PA1 a reinforcing film of a tough, flexible reinforcing material bonded to the adhesive film on the inner surface of the latter, the flexible reinforcing film comprising a material selected from the group of film-forming materials consisting of poly(ethylene terephthalate) and vulcanized fiber, PA1 (a) providing an elongated strip of a flexible backing material having complementary ends, at least one major surface, and having an abrasive layer attached to the major surface, the flexible backing material comprising at least one flexible support and a hot-melt adhesive layer; PA1 (b) abutting the complementary ends to provide a belt; PA1 (c) applying pressure and heat over an area of the abutting ends sufficient to cause the hot-melt adhesive to flow across the abutting complementary ends; and PA1 (d) allowing said heated area to cool, whereby the hot-melt adhesive is continuous over the abutting complementary ends and provides a splice; or PA1 (a) providing an elongated strip of a flexible backing material having complementary ends and having at least one major surface, the flexible backing material comprising at least one flexible support and a hot-melt adhesive layer; PA1 (b) abutting the complementary ends to provide a belt; PA1 (c) applying pressure and heat over an area of the abutting ends sufficient to cause said hot-melt adhesive to flow across the abutting complementary ends; and PA1 (d) allowing the heated area to cool, whereby the hot-melt adhesive is continuous over the abutting complementary ends and provides a splice; and PA1 (e) applying an abrasive layer to the major surface.
the flexible sheet base having a joint with abutting end portions cut at an angle of about 45.degree. relative to the side edges of the flexible base sheet, and the reinforcing film having a fused joint spaced longitudinally from the first joint and with abutting end portions cut at acute angles relative to the side edges thereof.